1. Field of the Invention
This invention pertains to driers used to dry printed matter and more particularly to drier cassettes, mounting brackets and expander units for drier cassettes used in these driers for printed matter.
2. Description of Related Art
In the prior art wetted printed matter, such as a paper web or paper sheets, are dried in a drier after production by passing the printed matter under a series of individually mounted drier cassettes situated within the drier housing. These driers are, for example, used to dry printed matter from a sheet-fed offset printing press.
A drier cassette is essentially a box having an interior, an air input port to that interior and a plurality of exhaust openings on at least one side. Gas or air is pumped through the air input port into the interior and exhausts through the exhaust openings on the side of the box. In typical use the exhaust openings of the drier cassettes are oriented downwardly so that the printed matter may be successively carried under the drier cassettes on a track or conveyor belt, through the exhausting gas. A guide pan that both supports and moves the printed matter is frequently used to position the wet printed matter. The guide pan is a type of track having a multiplicity of holes exhausting air upwardly to support and move the printed matter.
A drier cassette may also include one or more radiant heat emitters, such as infrared emitters, to increase drying efficiency. These radiant heat emitters are mounted on a side of the drier cassette having the exhaust openings. As the printed matter is passed under the drier cassette exhaust the radiant heat emitter additionally warms the printed matter to aid drying. The exhaust disperses the additional humidity generated by the heating of the printed matter and otherwise further aids in the drying process.
This type of drier, employing a plurality of drier cassettes, is sometimes referred to as an air knife drier. A typical air knife drier includes series of drier cassettes that are releasably mounted on brackets fixedly attached to the housing of the drier or to framework within the housing of the drier. Although this type of drier configuration is typically directed to drying printed matter, the term xe2x80x9cprinted matterxe2x80x9d as used herein is not limiting, but used as an example of a type of application to which the present invention may be applied. The invention might also be used for a sheet or ream of any material that may be dried or cooled after exiting a production unit or is otherwise amendable to being dried or cooled by an air knife drier, for example, the drying of fabric from a production unit producing a ream of fabric or other sheet material. The invention then, is not limited to any particular type of matter that may be dried.
The drying efficiency of using such a series of drier cassettes of the prior art is less than optimal, however, because the drier cassette mounting brackets present spaces or gaps between the drier cassettes where the printed matter is not exposed to either the radiant heating or to the exhausting gas or air. Moreover, as the printed matter passes under each successive drier cassette, the paper""s path is disturbed or disrupted as it successively encounters the exhaust of each individual drier cassette. This disruption in the paper path can cause the paper to flutter or be misdirected, leading to jamming and limiting the speed at which the paper can be passed under the exhaust.
The inefficiencies of air knife driers of the prior art have been attenuated or eliminated by providing an expander unit for drier cassettes that is not only also a support bracket, but performs many of the drying functions of the drying cassette itself, eliminating the gaps or spaces occurring between the drier cassettes held by brackets of the prior art.
In a broad aspect the invention encompasses providing an expander unit, which acts as a stationary bracket for a drier cassette and that is also an enclosed box like a drier cassette, has an interior and is adapted to be supplied with a flow of gas to the interior, and, exhausts the gas through a plurality of exhaust openings. The expander unit is fixedly attached to a surface of the housing or framework within the drier and is adapted to be joined to and support one or more drier cassettes.
Another aspect of this invention is a drier cassette that is adapted to function with one or more expander units. Like a drier cassette of the prior art, the drier cassette of the present invention is an enclosure having an interior adapted to be supplied with a flow of gas to the interior and the gas exhausts through a plurality of exhaust openings on a side of the drier cassette. When the drier cassette of the present invention is joined together with one or more expander units, with their respective exhaust openings oriented in the same direction, the combination of one or more expander units and drier cassettes create an uninterrupted path of drying exhaust gas for printed matter to travel through.
In one embodiment the gas is supplied to either a first drier cassette or a first expander unit by sharing the gas supplied to a second drier cassette or to an expander unit. In the case where gas is supplied to the second expander unit, the gas communicates into an adjoining drier cassette through a conduit or interfacing exhaust openings. A window aperture, for example, may be provided in an expander unit and also provided in an adjoined drier cassette, so that the gas may communicate between the expander unit and the joined drier cassette through the two window apertures.
In the preferred embodiment the expander units are each formed as a rectangular box having top, bottom, front, back and two lengthwise sides. One or more of the lengthwise sides is adapted to releasably join to and support a drier cassette and the bottom side of the box has a plurality of exhaust openings to exhaust the gas. The expander units are mounted within the drier with their exhaust openings facing downwardly.
Where only a single lengthwise side of an expander unit is adapted to releasably join to a drier cassette, this unit is termed an end expander unit. Where both lengthwise sides of an expander unit are adapted to releasably join to a drier cassette, this unit is termed an intermediate expander unit.
The drier cassettes of the preferred embodiment of the present invention are also each formed as a rectangular box having top, bottom, front, back and two lengthwise sides, and in the preferred embodiment each of the lengthwise sides is adapted to be releasably joined to the expander unit. The bottom side of the drier cassette also has a plurality of exhaust openings to exhaust the gas.
One or more drier cassettes and one or more expander units are joined such that their bottom sides are oriented in the same direction, so that the exhaust openings of drier cassettes are oriented in the same direction as the exhaust openings of the expander units, causing the gas of these units to be exhausted in the same direction. Heat emitters, for example infrared tubes, are provided on the bottom side of the expander unit and are also provided on the bottom side of the drier cassette to enhance the drying process.
A series of drier cassettes releasably joined to expander units creates a cassette expander unit system for a drier for drying printed matter. Paper is moved in a direction under the cassette expander unit system. The series of drier cassettes and expander units comprises, discussed in the direction of paper flow, an end expander unit having a single window aperture in a single lengthwise side. This end expander unit is affixed to the housing or framework of the drier and releasably joined to support a drier cassette. The end expander unit is joined to a drier cassette having window apertures in both lengthwise sides, wherein each lengthwise side is formed to releasably join to and be supported by an expander unit. A second end expander unit having a single window aperture is releasably joined to the other side of the drier cassette, completing a simple cassette expander unit system.
In most driers, however, two or more drier cassettes are used. This necessitates the need for an intermediate expander unit having window apertures in both of its lengthwise sides in order to join two drier cassettes, one on each side. In this manner a series of drier cassettes and expander units can be releasably joined to create a continuous unit exhausting gas. For example, again discussed in the direction of paper flow, a first end expander unit is releasably joined to a first drier cassette. The first drier cassette is also releasably joined to an intermediate expander unit distal the first end expander unit. The intermediate expander unit is releasably joined to a second drier cassette distal the first drier cassette. The second drier cassette is also releasably joined to a second end expander unit, completing the system. In the preferred embodiment the end and intermediate expander units are fixedly attached to the drier housing or framework within the housing and the drier cassettes are inserted and removed from between the expander units.
Two such drier cassettes may, alternatively, be releasably joined directly to each other if the support of an intermediate expander unit support is not required.
Gas or air may be supplied to each expander unit and drier cassette with a separate air input port on each expander unit and drier cassette. If gas is supplied to all of the drier cassettes and the expander units through separate air input ports the window apertures may be eliminated because there is no need for gas to communicate between neighboring units through adjoining window apertures. In the preferred embodiment gas or air is only provided to the drier cassettes through an air input port on each drier cassette. Each expander unit includes a window aperture in the lengthwise side or sides of the expander unit that joins to a drier cassette, each drier cassette has a complementary window aperture in the lengthwise sides of the drier cassette that join to expander units.
In this manner when gas or air is supplied to the drier cassettes the gas will communicate to the adjoining expander units to supply the expander units with gas or air. When gas is supplied to the cassette expander unit system components in such an alternating configuration, supplying the drier cassettes only, or, supplying the expander units only, the units that are not supplied with gas or air should best have a containment wall subdividing the interior of the length of the box. The containment wall allows the interior gas pressure, and hence exhaust pressure, to be more easily maintained by limiting the total volume of the combined interiors of joined drier cassettes and expander units, which are to be supplied with a given air input. In embodiments where air or gas is instead supplied to an expander unit, and shared with a cassette drier, this containment wall will likely need to be placed to lengthwise divide the adjoining drier cassettes instead. The containment wall will be needed in most applications, but the requirement for this wall is a function of the required pressure for the application and the total volume of the chamber being supplied by a given volume of gas or air at a given pressure. This need for a containment wall may be determined for a particular application by simple application of design principals by one of ordinary skill in the art.
As printed matter travels in the guide pan towards the cassette expander unit system it encounters the leading edge of the combined exhaust of the series of releasably joined cassette driers and expander units, i.e. of a cassette expander unit system. The leading edge is the exhaust is generated through the outermost exhaust openings of the end unit. In most configurations the leading edge is the first exhaust openings exhaust generated by a first end expander unit encountered by the paper. With use of a guide pan the paper is carried on an upward cushion of air to under the cassette expander unit system. Upon encountering the downward exhaust at the leading edge the paper may ruffle and shift as the opposing upward and downward flows of air achieve equilibrium, causing a disruption in the path of the paper. The same phenomenon may occur when the printed matter exits the combined exhaust at the trailing edge, under the last, typically second, end expander unit.
The end units of a cassette expander unit system, whether they be drier cassettes or expander units, may be adapted to vary the exhaust emitted by them in order to control the disruption caused to the printed matter as it travels under the exhaust. One method and configuration calculated to attenuate this problem is adapting the unit, typically a first end expander unit, having the exhaust openings of the leading edge, to gradually increase the exhaust pressure on the printed matter as it travels from the leading edge towards the adjoining unit. Likewise, the unit at the trailing edge, typically a second end expander unit, may be adapted to gradually decrease its exhaust pressure on the printed matter as it exits the exhaust of the cassette expander unit system. Providing this pressure gradient at the leading and trailing edges of the cassette expander unit system decreases the ruffling of the printed matter as encounters the exhaust of the cassette expander unit system.
There are several ways to achieve this pressure gradient, and, more generally, to achieve any pressure variance in the cassette expander unit system. The exhaust openings of the leading and trailing edge end units of the cassette expander unit system, for example, may be provided with exhaust openings progressively increase in size or number from proximal to distal the exhaust openings of the leading edge. In this way a progressively greater downward exhaust is provided as the moving printed matter enters the exhaust at the leading edge of the combined exhaust, attenuating an abrupt change in downward exhaust pressure. In a similar manner progressively less downward exhaust is provided as the paper approaches the trailing edge of the combined exhaust, by configuring the second or last unit having the exhaust openings of the trailing edge with progressively smaller or fewer exhaust openings from distal to proximal the trailing edge.
In another embodiment, where an end unit is separately supplied with gas or air from an input port, that separate gas or air supply can be varied to increase or decrease the exhaust of that end unit.
In yet another embodiment, where the end units are supplied with gas or air from an adjoining unit, occluding chokes may be provided in the adjoining window apertures of a drier cassette and an end expander unit to limit the gas being shared with the end unit, thereby lessening the exhaust pressure.
In another yet embodiment the exhaust flow through the exhaust openings of an end expander unit is regulated by an occluding mask adapted to cover and occlude the exhaust openings. When the mask is moved over the exhaust openings the exhaust pressure of the end unit is decreased.
The drier cassettes and expander units may be releasably joined by a number of means. In the preferred embodiment a dovetail joint is used to join the lengthwise sides of the drier cassettes and the expander units that are adapted to be releasably joined. In the preferred embodiment one complementary half of the dovetail joint is machined into a drier cassette while the other complementary half of the dovetail joint is machined into an expander unit.
A method for drying printed matter is also provided, using the above apparatus. The method comprises the steps of providing a cassette expander unit system as described above, wherein the cassette expander unit system includes at least one expander unit; providing gas or air to the interior of one or more of the drier cassettes and expander units used, and, passing printed matter through the resulting exhaust through the exhaust openings of the cassette expander unit system.
One embodiment of the method for drying printed matter can be implemented by including an air input port on each expander unit to supply the interior of each expander unit with gas and also including an air input port on each drier cassette to supply the interior of each drier cassette with gas.
Alternatively in the method of the present invention an adjoining drier cassette and expander unit may share gas supplied to either through the use of conduits or apertures connecting an adjoining expander unit and drier cassette, allowing the gas to communicate therebetween. In the preferred method one or both lengthwise sides of an expander unit includes a window aperture and that lengthwise side is releasably joined to the lengthwise side of a drier cassette that also has a window aperture in its adjoined lengthwise side, whereby when gas is supplied to either it communicates between the interior of the drier cassette and the interior of the expander unit. This method eliminates the need for an air input port on each drier cassette and expander unit because the gas may be shared among the various components of the cassette expander unit system.
The method for drying printed matter may further include the step of using expander units that are regulated to emit gas at an exhaust pressure that is different from that of a drier cassette, at the leading and trailing edges of the cassette expander unit system. The various embodiments of such attenuated pressure end expander units, described above, may be used to achieve this.
In the preferred method all of the drier cassettes and any intermediate expander units have window apertures in both of their lengthwise sides, and, the end expander units having apertures in a single lengthwise side. The components are releasably joined to create a continuous unit to generate a more continuous exhaust to dry the paper because the gas can communicate between all adjoining expander units and drier cassettes.
Another aspect of the present invention is the method of passing printed matter under a drier of the construction recited above. A cassette expander unit system is provided, for a drier for drying printed matter, as described above. A supply of gas or air is provided to providing a supply of gas to one or more expander units acting as brackets and one or more drier cassettes, in order to cause one or more of the interiors of the drier cassettes and expander units to receive the gas and exhaust it through the unit""s openings. The cassette expander unit system may be, for example but not by limitation, any of the above embodiments or their equivalents. Printed matter is then passed through the resulting exhaust from the exhaust openings of the drier cassettes and expander units to dry the printed matter more efficiently with a continuous path of air or gas.
This method may further include the step of attenuating the exhaust pressure of the drier cassettes or expander units at one or both ends of the air knife drier to attenuate the disruption to the paper path caused by the downward exhaust of the drying units. Typically the pressure at the leading and trailing edges of the paper path will be less so as to create a pressure gradient that gradually rises and falls as the paper passes through the exhaust. This gradient may be achieved by any of the above described embodiments or equivalent embodiment, for example but not limited to by providing exhaust openings in the bottom side of the box that progressively increase in size from distal to proximal the lengthwise side having a window aperture; by providing exhaust openings in the bottom side of the box that progressively increase in density from distal to proximal the lengthwise side having a window aperture; by providing a choke or an occluding mask adapted to cover and occlude the exhaust openings.
Together, one or more expander units joined to one or more drier cassettes, joined to allow gas or air to be exhausted from both a drier cassette and the an expander unit, comprise a cassette expander unit system for a drier for drying printed matter.
Another aspect of the present invention is the method of passing printed matter under a drier of the construction as recited in this description. A cassette expander unit system is provided, for a drier for drying printed matter, as described above. A supply of gas or air is provided to providing a supply of gas to one or more expander units acting as brackets and one or more drier cassettes, in order to cause one or more of the interiors of the drier cassettes and expander units to receive the gas and exhaust it through the unit""s openings. The cassette expander unit system may be, for example but not by limitation, any of the above embodiments or their equivalents. Printed matter is then passed through the resulting exhaust from the exhaust openings of the drier cassettes and expander units to dry the printed matter more efficiently with a continuous path of air or gas.
This method may further include the step of attenuating the exhaust pressure of the drier cassettes or expander units at one or both ends of the air knife drier to attenuate the disruption to the paper path caused by the downward exhaust of the drying units. Typically the pressure at the leading and trailing edges of the paper path will be less so as to create a pressure gradient that gradually rises and falls as the paper passes through the exhaust. This gradient may be achieved by any of the above described embodiments or equivalent embodiment, for example but not limited to by providing exhaust openings in the bottom side of the box that progressively increase in size from distal to proximal the lengthwise side having a window aperture; by providing exhaust openings in the bottom side of the box that progressively increase in density from distal to proximal the lengthwise side having a window aperture; by providing a choke or an occluding mask adapted to cover and occlude the exhaust openings.